The present invention relates to golf clubs and, more particularly, to a golf club that has an insert on the strike surface of the club formed from the conversion reaction of an amount of polybutadiene, a free radical source, and a cis-to-trans catalyst at a sufficient reaction temperature to form a polybutadiene reaction product.
Golf clubs have long been developed to improve the xe2x80x9ctouchxe2x80x9d and xe2x80x9cfeelxe2x80x9d of the club, most particularly with, but not limited to, the clubs used on and around the green, such as a putter. One approach to improve the touch and feel of a club is to modify either the grip, the shaft, or the head of the golf club, in particular, the strike face of the head. For example, modifications to the club head could include an insert that is placed on the club head strike surface to affect the impact of the club with the golf ball and to improve the sensory feedback to the golfer during and subsequent to impact.
A number of club face insert materials have been employed by golf club manufacturers in an effort to improve the touch and feel of golf clubs, such as metals, plastics, alloys, rubbers, and ceramics. A few exemplary such references are discussed below.
U.S. Pat. No. 5,332,214 discloses a golf putter having an elastomeric striking face secured to a support member and a weight within a recessed cavity. The preferred elastomeric material is HYTREL(copyright), a polyester elastomer commercially available from E.I. DuPont de Nemours and Co. of Wilmington, Del.
U.S. Pat. No. 5,485,997 discloses a putter head having a recess in the front face, the recess containing a face plate constructed of a non-metallic material, such as an elastomer, a synthetic resin, or glass.
U.S. Pat. No. 5,524,331 discloses a method for manufacturing a golf club head including a recess containing a curable, non-metal insert, such as a void-free epoxy impregnated carbon fiber sheet, ambient temperature resins, UV curable resins, thermosetting polymers, and/or thermoplastic polymers.
U.S. Pat. No. 5,575,472 discloses a golf putting head having a recessed cavity on its front face that includes a raised perimeter bead. An insert is cast within the cavity and the club face is finished to provide a smooth planar surface. The insert material is preferably a polymeric or elastomeric material, ambient temperature resins, UV curable resins, thermosetting polymers, and/or thermoplastic polymers.
U.S. Pat. Nos. 5,605,510 and 5,460,377 are directed to a golf putter having a non-metallic face, typically consisting of synthetic resin or lightweight plastic.
U.S. Pat. No. 5,674,132 discloses a golf club having a resilient insert comprising one or more laminations. Preferably, the insert is made of a synthetic polymer material, such as solid polyurethane, having a hardness in the range of 70 Shore A to 70 Shore D.
U.S. Pat. No. 5,690,562 discloses a golf putter head having an insert in the front face, the insert being constructed of an elastomeric material having a Durometer value of at least about 60 Shore D.
U.S. Pat. No. 5,718,644 discloses an insert member for a golf putter, the insert comprising a regular, elongated curved surface, such as an arc section of a cylinder. The insert is comprised of titanium, titanium alloy, anodized aluminum, or high strength plastic.
U.S. Pat. No. 5,842,935 discloses a golf putter head that includes a low density insert disposed in a cavity formed in a body. The insert is preferably formed of polyurethane having a Shore D hardness of 65.
U.S. Pat. No. 5,921,871 discloses a golf putter having a resilient insert having a controlled rebound factor fitted into a wedge-shaped recess in the face of the putter head. The insert pad is preferably made of a synthetic polymer material, such as polyurethane having a hardness in the range of 70 Shore A to 80 Shore D.
U.S. Pat. No. 5,924,939 discloses a golf club head having a two-layered insert preferably comprising a thermoset rubber, such as one formed from a cured mixture comprising a polymer blend, a metal salt of an unsaturated carboxylic acid, a free radical initiator, and silica.
U.S. Pat. No. 5,931,743 discloses a club head for a golf club having a resilient member on the front face, the resilient member preferably comprising a polyurethane elastomer exhibiting zero compression for imparting top spin to a golf ball.
U.S. Pat. No. 6,030,294 discloses a method of making a golf club head or an insert for a golf club head which comprises preparing a porous base selected from the group consisting of metals, metal alloys, and cements, and coating at least the face of the base with a plastic material, such as monomers, polymers, urethanes, epoxies, lacquers, paints, and the like.
PCT Publication No. WO 00/20076 discloses a golf club head having a polyether block amide insert that has a Shore A hardness of at least 90 and a rebound factor of at least 60%.
Another resilient yet durable material, commonly used in the various layers and cores of golf balls, is polybutadiene and, in particular, polybutadiene having a high cis-isomer polybutadiene concentration. In general, various polybutadiene compositions are used in golf balls, and some of these core compositions are discussed below.
U.S. Pat. No. 3,239,228 discloses a solid golf ball having a core molded of polybutadiene rubber with a high sulfur content, and a cover. The polybutadiene content of the core is stereo-controlled to the configuration 25-100 percent cis- and 0-65 percent trans-1,4-polybutadiene, with any remainder having a vinyl configuration of polybutadiene. A preferred embodiment of the polybutadiene golf ball core contains 35 percent cis-, 52 percent trans-, and 13 percent vinyl-polybutadiene.
U.S. Pat. Nos. 3,572,721 and 3,572,722 disclose a solid, one- or two-piece golf ball, with the two-piece ball having a core and a cover. The cover material can include any one of a number of materials, or blends thereof, known to those of ordinary skill in the art, including trans-polybutadiene which may be present in an amount from at least 90 percent, with the remainder being the cis- and/or vinyl configuration.
U.S. Pat. No. 3,992,014 discloses a one-piece, solid golf ball. The golf ball material is typically polybutadiene, with a stereo-configuration selected to be at least 60 percent cis-polybutadiene, with the remaining 40 percent being the trans-polybutadiene and/or 1,2-polybutadiene (vinyl) isomers.
U.S. Pat. No. 4,692,497 discloses a golf ball and material thereof formed by curing a diene polymer including polybutadiene and a metal salt of an alpha, beta ethylenically unsaturated acid using at least two free radical initiators.
U.S. Pat. No. 4,931,376 discloses a process for producing butadiene polymers for use in various applications, including golf ball cover materials. One embodiment of the invention employs a blended polymeric resin material, including at least 30 percent by weight of a trans-polybutadiene polymer as a golf ball cover on a two-piece ball. In a preferred embodiment, the golf ball cover material contains a blend including 30 to 90 percent by weight of a trans-polybutadiene polymer.
U.S. Pat. No. 4,971,329 discloses a solid golf ball made from a polybutadiene admixture of cis-1,4 polybutadiene and 1,2 polybutadiene, a metal salt of an unsaturated carboxylic acid, an inorganic filler, and a free radical initiator. The admixture has about 99.5 percent to about 95 percent by weight of cis-1,4 polybutadiene and about 0.5 percent to about 5 percent by weight of 1,2 polybutadiene.
U.S. Pat. No. 5,252,652 discloses a one-piece or multi-layered golf ball core with improved flying performance from a rubber composition comprising a base rubber, preferably 1,4-polybutadiene with a cis-content of at least 40 mole percent, an unsaturated carboxylic acid metal salt, an organic peroxide, and an organic sulfur compound and/or a metal salt thereof. The organic sulfur compound and/or a metal salt is typically present in an amount from about 0.05 to 2 parts per hundred by weight and the organic peroxide is typically present in an amount from about 0.5 to 3 parts per hundred by weight of the total polymer component.
U.S. Pat. No. 5,421,580 discloses a wound golf ball having a liquid center contained in a center bag, a rubber thread layer formed on the liquid center, and a cover over the wound layer and liquid center. The cover material can include any one of a number of materials, or blends thereof, known to those of ordinary skill in the art, including trans-polybutadiene and/or 1,2-polybutadiene (vinyl), such that the cover has a JIS-C hardness of 70-85; preferred trans-percentages are not disclosed.
U.S. Pat. No. 5,697,856 discloses a solid golf ball having a core and a cover wherein the core is produced by vulcanizing a base rubber composition containing a butadiene rubber having a cis-polybutadiene structure content of not less than 90 percent before vulcanization. The amount of trans-polybutadiene structure present after vulcanization is 10 to 30 percent, as amounts over 30 percent are alleged to detrimentally result in cores that are too soft with deteriorated resilience performance, and to cause a decrease in golf ball performance. The core includes a vulcanizing agent, a filler, an organic peroxide, and an organosulfur compound.
U.S. Pat. No. 5,816,944 discloses a solid golf ball having a core and a cover wherein the core has a JIS-C hardness of 50 to 80 and the cover has a Shore-D hardness of 50 to 60. The core material includes vulcanized rubber, such as cis-polybutadiene, with a crosslinker, an organic peroxide, an organosulfur compound and/or a metal-containing organosulfur compound, and a filler.
European Patent No. 0 577 058 discloses a golf ball containing a core and a cover that is formed as two separate layers. The inner layer of the cover is molded over the core and is formed from ionomer resin. The outer layer of the cover is molded over the inner layer and is formed from a blend of natural or synthetic balata and a crosslinkable elastomer, such as polybutadiene. In one embodiment of the outer layer of the cover, the elastomer is 1,4-polybutadiene having a cis-structure of at least 40 percent, with the remaining 60 percent being the trans-isomer. A preferred embodiment contains a cis-structure of at least 90 percent and more preferably, a cis-structure of at least 95 percent.
British Patent No. 1,168,609 discloses a molding composition from which improved golf ball cores can be molded and which contains cis-polybutadiene as a basic polymer component. The core polymer component typically includes at least 60 percent cis-polybutadiene, with the remainder being either the trans- or vinyl-forms of polybutadiene. In a preferred embodiment, the core polybutadiene component contains 90 percent cis-configuration, with the remaining 10 percent being either the trans- or vinyl-configurations of 1,4-polybutadiene.
British Patent No. 1,209,032 discloses a two- or three-piece golf ball having a core and a cover. The core or cover material can be any material capable of being crosslinked. In particular, the material can be a polymer or a copolymer of butadiene or isoprene. Preferably, the polymer component is polybutadiene having a cis content of greater than 50 percent by weight.
British Patent No. 2,321,021 discloses a solid golf ball having a core and a cover formed on the core and having a two-layered cover construction having an inner cover layer and an outer cover layer. The outer cover layer is comprised of a rubber composite that contains 0.05 to 5 parts by weight of an organic sulfide compound. The core rubber composition comprises a base rubber, preferably 1,4-polybutadiene having a cis-content of at least 40 percent by weight, a crosslinking agent, a co-crosslinking agent, an organic sulfide, and a filler.
Additionally, conventional polymers that have a high percentage of the trans-polybutadiene conformation, such as DIENE(copyright) 35NF, from Firestone Corp., that has 40 percent cis-isomer and 50 percent trans-polybutadiene isomer, and mixtures of high-cis- and high-trans-polybutadiene isomers, such as CARIFLEX(copyright) BR1220, from Shell Corporation, and FUREN(copyright) 88, from Asahi Chemical Co., respectively, typically do not yield high resilience values.
Thus, it is desired that the present invention provide an improved golf club head, for example, with better touch and feel as a result of modifying the strike face of the golf club head.
The invention relates to a golf club having a toe and an opposite heel, a sole portion and an opposite top portion, a forwardly facing exposed strike face, an opposite rearwardly facing exposed back face portion, a hosel, and a shaft, including a recess defined in the strike face, said recess having at least a bottom surface spaced from the back face portion and a side wall surface extending between the bottom surface and the strike face; and an insert located in the recess formed of a first vibration dampening material including an insert material formed from the conversion reaction of a resilient polymer having sufficient amounts of polybutadiene, a free radical source, and a cis-to-trans catalyst, which reaction occurs at a sufficient temperature to form a polybutadiene reaction product which comprises an amount of trans-polybutadiene isomer greater than the amount of trans-polybutadiene isomer present before the conversion reaction.
In one embodiment, the insert material has a first dynamic stiffness measured at xe2x88x9250xc2x0 C. that is less than about 130 percent of a second dynamic stiffness measured at 0xc2x0 C. In another embodiment, the insert has a midpoint having a first amount of trans-polybutadiene and a surface having a second amount of trans-polybutadiene, wherein the first amount is at least about 6 percent less than the second amount.
In one embodiment, the cis-to-trans catalyst includes a Group VIA element, an inorganic sulfur compound, an organosulfur compound, an aromatic organometallic compound, a metal-organosulfur compound, or an aromatic organic compound, or a combination thereof. In one preferred embodiment, the cis-to-trans catalyst includes a Group VIA element, an organosulfur component, an inorganic sulfide, or a combination thereof. Typically, the cis-to-trans catalyst is present in an amount from about 0.01 to about 25 parts per hundred of resilient polymer. In another preferred embodiment, the cis-to-trans catalyst is present in an amount from about 0.01 to about 15 parts per hundred of the total resilient polymer component. In yet another preferred embodiment, the cis-to-trans catalyst is present in an amount from about 0.05 to about 5 parts per hundred of polybutadiene.
In one preferred embodiment, the insert material includes less than about 7 percent vinyl isomer content based on the total polybutadiene. In a more preferred embodiment, the insert material includes less than about 4 percent vinyl isomer. In one more preferred embodiment, the insert material includes less than about 2 percent vinyl isomer.
In one embodiment, the club includes a plurality of apertures extending from said back face portion toward the recess and a second vibration dampening material located in at least one of the apertures. In another embodiment, the insert further includes a back face and the back face is spaced from said bottom surface of the recess to define a gap. In one embodiment, the club further includes a second vibration dampening material located within the gap. In a preferred embodiment, the second vibration material is disposed within at least a majority, or preferably all, of the apertures. In yet another preferred embodiment, the second vibration dampening material includes the insert material.
The invention also relates to a golf club insert including an insert material formed from the conversion reaction of a sufficient amount of a resilient polymer including polybutadiene, a free radical source, and a cis-to-trans catalyst, which reaction occurs at a sufficient temperature to form a polybutadiene reaction product which comprises an amount of trans-polybutadiene greater than the amount of trans-polybutadiene present before the conversion reaction. In one embodiment, the insert material has a first dynamic stiffness measured at xe2x88x9250xc2x0 C. that is less than about 130 percent of a second dynamic stiffness measured at 0xc2x0 C.
In one embodiment, the insert has a midpoint having a first amount of trans-polybutadiene and a surface having a second amount of trans-polybutadiene, wherein the first amount is at least about 6 percent less than the second amount.
In another embodiment, the cis-to-trans catalyst includes a Group VIA element, an inorganic sulfur compound, an organosulfur compound, an aromatic organometallic compound, a metal-organosulfur compound, an aromatic organic compound, or a combination thereof. In one preferred embodiment, the cis-to-trans catalyst includes a Group VIA element, an organosulfur component, an inorganic sulfide, or a combination thereof. One preferred cis-to-trans catalyst includes 4,4xe2x80x2-ditolyl disulfide. The cis-to-trans catalyst is typically present in amounts similar to those noted above.
The insert material preferably includes less than about 7 percent vinyl isomer content based on the total polybutadiene. In one preferred embodiment, the insert material includes less than about 4 percent vinyl isomer. In another preferred embodiment, the insert material includes less than about 2 percent vinyl isomer.
The invention also relates to a method for forming a golf club insert which includes combining a cis-to-trans catalyst, a free radical source, and a first resilient polymer component comprising a polybutadiene component having cis-isomer present in an amount greater than about 70 percent of the total polymer component; converting a portion of the first resilient polymer component to a second resilient polymer component at a temperature sufficient to convert at least a portion of the cis-polybutadiene isomer to a trans-polybutadiene isomer; and forming the second resilient polymer component into at least a portion of the golf club insert.
In one preferred embodiment, the portion of the second resilient polymer component is formed into a substantially rectangular shape. In another embodiment, the portion of the second resilient polymer component is formed by molding the insert in situ on a golf club. In one embodiment, the polybutadiene component includes a cis-polybutadiene isomer present in an amount of at least about 80 percent of the total first resilient polymer component. It is also possible to combine a density-modifying filler, a crosslinking agent, or both with the insert material.
In one embodiment, the insert has a midpoint having a first amount of trans-polybutadiene and a surface having a second amount of trans-polybutadiene, wherein the first amount is at least about 7 percent less than the second amount. In another embodiment, the second amount of trans-polybutadiene component is selected to include a vinyl polybutadiene component present in an amount of less than about 7 percent of the total resilient polymer component.
The method can use similar types and amounts of cis-to-trans catalyst as noted above for the insert and club embodiments. In one embodiment, the converting takes about 2 to 18 min. In a preferred embodiment, the converting includes a single-step compression molding of the first resilient polymer component to convert the first resilient polymer component to the second resilient polymer in about 3 to 15 minutes; and the forming includes shaping the second resilient polymer component into a substantially rectangular shape. In one preferred embodiment, the converting and forming are substantially simultaneous.